1. Field of the Invention
The present invention relates to improvement in visual axis detecting apparatus and optical equipment for detecting a visual axis of an observer.
2. Related Background Art
Various proposals have been made heretofore on cameras adapted to detect the direction of the visual axis of a photographer (observer) to determine which area (position) the photographer is observing in the finder field, i.e., to determine the gazing direction of the photographer by visual axis detecting means mounted in part of the camera and control various photographing functions such as autofocusing, auto-exposure, etc. on the basis of a signal from the visual axis detecting means.
For example, Assignee of the present application proposed the camera equipped with visual axis detecting means for detecting the photographer""s gazing direction and automatic exposure control means having a plurality of photometric sensitivity distributions and adapted to control driving of focus detecting means and the automatic exposure control means on the basis of the output signal from the visual axis detecting means, in Japanese Patent Application Laid-Open No. 01-241511 (U.S. Pat. No. 5,486,892).
In use of any equipment with the visual axis detecting function besides the above-stated cameras, the observer gazes at an indication in an area to be selected on a display section of the equipment and this gazing action itself is a factor to make a big error in detection of the visual axis.
Namely, since the ability of gazing at a point or in a direction for a predetermined duration differs depending upon individuals, there occurred cases where a certain person was able to select an objective area but another person failed to select it though they were gazing the indication in the area to be selected on the display section of the equipment with the visual axis detecting function.
Namely, the variation in the ability of gazing at a point or in a direction for a predetermined duration was a great hurdle that anyone had to surmount in order to manipulate the visual axis detecting function.
As a solution to the above problem, Assignee proposed a technique of dividing the interior of the screen into plural areas, performing a plurality of visual axis detections, and determining a gazing point and area on the basis of frequencies and residence durations of existence of the visual axis position in the respective areas, in Japanese Patent Application Laid-Open No. 04-101126 (U.S. Pat. No. 5,857,120). Namely, the purpose of the technique is to average and stabilize the variation of the visual axis position by sampling a plurality of visual axis positions.
However, constant execution of consecutive visual axis detections necessitated some time for finally determining the visual axis position, which resulted in the drawback of deterioration of response as the visual axis detecting equipment.
Assignee of the present application proposed the camera with the visual axis detecting function adapted to select a region in a photographing field to obtain information for control of various operations of the camera on the basis of the output from the visual axis detecting means, wherein the selection areas were switched according to reliability of the output from the visual axis detecting means, Japanese Patent Application Laid-Open No. 06-308373. The number of selectable areas is switched, for example, so that the number of areas available for the selection is switched to three out of five original selectable areas when the reliability of the visual axis is low.
The reliability of the visual axis detecting means stated herein refers to the result of evaluation of the contrast of an eye image, the size of the pupil, or the positions of Purkinje images and the center of the pupil calculated. The determination of reliability of these is actually effective in the case where the eye image itself is temporarily defective for some reason. Therefore, it was not a solution to the variation of the visual axis position caused by the difference of the gazing ability originally being the physiological problem of men as described at the beginning.
An object of the present invention is to provide visual axis detecting apparatus and optical equipment permitting each user to select an intended area while minimizing influence of the variation in the visual axis position due to the individual difference of the gazing ability.
An aspect of the present invention is a visual axis detecting apparatus comprising:
a visual axis detection circuit for detecting a visual axis of an observer;
an arithmetic circuit for performing an arithmetic operation of calculating a distributed state of variations of visual axis positions obtained in a plurality of visual axis detections executed by the visual axis detection circuit in a state in which the observer is observing a predetermined point, with respect to the predetermined point;
a determination circuit for determining a condition of the visual axis according to the result of detection by the visual axis detection circuit; and
a change circuit for changing a determination process of determining the condition of the visual axis by the determination circuit, according to the distributed state of variations.
Preferably, the visual axis detecting apparatus further comprises a storage circuit for storing the distributed state calculated by the arithmetic circuit, wherein the change circuit changes the number of detections by the visual axis detection circuit to a smaller number when the distributed state of variations is small, but the change circuit changes the number of detections by the visual axis detection circuit to a larger number when the distributed state of variations is large, and wherein said determination circuit determines the condition of the visual axis on the basis of the number of detections changed by the change circuit.
Preferably, the determination circuit determines that a position of the visual axis is an average position of a plurality of visual axis positions detected by the visual axis detection circuit.
Preferably, the arithmetic circuit calculates a standard deviation of a plurality of visual axis positions.
Preferably, the predetermined point is displayed on a screen.
Preferably, a plurality of zones are displayed on the screen and a zone is selected out of the plurality of zones according to the condition of the visual axis determined by the determination circuit.
Preferably, the screen is a focusing screen of a camera.
Preferably, the apparatus further comprises a mode setting member for setting a mode of performing the arithmetic operation by the arithmetic circuit and a mode of performing the determination by the determination circuit.
Another aspect of the present invention is a visual axis detecting apparatus comprising:
a screen in which a plurality of zones are formed;
a visual axis detection circuit for detecting a visual axis of an observer;
an arithmetic circuit for performing an arithmetic operation of calculating a distributed state of variations of visual axis positions obtained in a plurality of visual axis detections executed by the visual axis detection circuit in a state in which the observer is observing a predetermined point on said screen, with respect to the predetermined point;
a selection circuit for selecting one of the plurality of zones according to the result of detection by the visual axis detection circuit; and
a change circuit for changing a selection process by the selection circuit according to the distributed state of variations.
Other features of the present invention will become apparent on the basis of the drawings and description of the preferred embodiments which will follow.